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News Release

Jacobs School Hard Disk Pioneer Elected to National Academy of Engineering

San Diego, CA, February 08, 2008 -- UC San Diego Jacobs School of Engineering professor Paul Siegel – a leading authority on coding for hard disk magnetic recording systems – has been elected to the National Academy of Engineering "for the invention and development of advanced coding techniques for digital recording systems."

Paul Siegel

Prof. Paul Siegel is the latest Jacobs
School professor to be elected to
the National Academy of Engineering.
He holds a CMRR Endowed
Professorship at UCSD. 

Prof. Siegel is an electrical engineering professor and the director of UCSD’s Center for Magnetic Recording Research (CMRR) – a collaboration between UCSD, companies in the magnetic recording industry and government agencies. The CMRR mission is to advance the state-of-the-art in magnetic storage, and to produce highly trained graduate students and postdoctoral professionals. 

In the 1980s and early 1990s, Siegel was part of an IBM team that helped to revolutionize the hard disk industry through advances in signal processing. Siegel’s work on signal processing systems has increased the reliability of information retrieval from hard disk drives. His patents and publications provided part of the framework for the introduction of a signal processing approach called “coded partial response, maximum likelihood” (PRML) which is used in every disk drive today. 

PRML, along with the introduction of advanced heads and disks, enabled the extremely rapid growth in capacity of magnetic hard disk drives. A one gigabyte hard disk drive in 1984 cost approximately $50,000 and was the size of a small washing machine. Today, mp3 players like iPods contain drives with 30 times this capacity and these are small drives by today’s standards.

For information to be stored on a hard disk, electronic signals carrying the data first travel down a wire to one of the disk’s writing heads. To record this information, the write heads leak flux which results in information stored on the disk.

Retrieval of this stored information requires a read head flying very close to the disk to read the information as pulses. These pulses must be converted back to electronic signals in an ultra reliable way – and this is where Siegel’s work enters the picture.  

Hard disk storage capacity is increased by packing more bits per unit of surface area. This increased density causes interference among read pulses – a phenomenon known as intersymbol interference or ISI – and makes reliable retrieval of data from hard disks more challenging.

One way to deal with ISI would be to narrow the pulses to reduce interference among pulses, but this increases the noise. Another approach could be to increase the space between bits on the hard disk thus increasing the inter-pulse distance – but that is counterproductive to the goal of increasing a disk’s storage capacity.

Siegel was part of the IBM team that came up with a powerful solution to the ISI problem using signal processing called “modulation coding.” In particular, he was the co-inventor of a kind of modulation code called “spectral null codes.” This was the first comprehensive class of codes that allowed PRML systems to operate at a lower signal-to-noise ratio than uncoded PRML systems. He also invented a decoder for these codes that was much simpler than the optimal decoder but gave essentially the same performance.

hard disk

Photograph of an old-style hard disk,
courtesy of Prof. Jack Keil Wolf

With this work, Siegel demonstrated that ISI complications to the read process can be mitigated with signal processing. He and his collaborators showed that you can control this interference and then use the Viterbi algorithm to unscramble the PRML.

“Paul worked on finding codes that give better performance when the PRML is unscrambled by the Viterbi detector,” said Jack Keil Wolf, the Stephen O. Rice Professor of Magnetics at the Department of Electrical and Computer Engineering at the Jacobs School.

The Viterbi algorithm and detector are named after their inventor, Andrew Viterbi, a co-founder of both Linkabit Corporation and Qualcomm Inc. In the 1970s and 1980s, Viterbi spent time as a UCSD professor while working at Linkabit and later at Qualcomm. He is now an Emeritus Professor at UCSD.

“Paul’s early work at IBM was on both modulation codes and error correction codes. He showed that you want to prevent certain sequences from being written on the disk, even if those sequences correspond to the data. For example, if you write all zeros, nothing will come off the drive when you read it and this means you lose the timing, and you want to avoid that,” said Wolf who is also a member of the National Academy of Engineering and leader of the Signal Processing Group within UCSD’s CMRR.

More recently, Dr. Siegel introduced iterative techniques for applications in storage. Several manufacturers are now developing read-write chips which utilize this principle. At CMRR, Siegel oversees research activities on a wide range of issues related to digital data storage and communications. He leads the Signal Transmission and Recording Group (STAR) at UCSD and participates in UCSD’s Center for Wireless Communications(CWC). Siegel is also an academic participant in the UCSD division of Calit2, and led the networked infrastructure "layer" during the institute's formative years. As an information theorist, Siegel is also a faculty member of Calit2's Information Theory and Applications Center (ITA), and has been a co-principal investigator on Calit2 research projects, including Ericsson-funded projects on CDMA systems and space-time processing for wireless.  

The current list of UCSD Jacobs School of Engineering NAE members is below:

Asbeck, Peter M.
Chien, Shu
Conn, Robert
Fung, Yuan-Cheng B.
Jin, Sungho
Lemke, James
Libby, Paul A.
Nemat-Nasser, Sia
Palsson, Bernhard O.
Penner, Stanford S.
Rumsey, Victor H.
Schmid-Schoenbein, Geert W.
Seible, Frieder
Siegel, Paul
Smarr, Larry L.
Talke, Frank E.
Watson, John T.
Williams, Forman A.
Wolf, Jack Keil
Viterbi, Andrew


Paul Siegel's Capsule Bio:

Paul Siegel was the manager of the Digital Processing and Coding project at the IBM Almaden Research Center from 1984 to 1993, a period when IBM was the world’s leader in the development of high density disk drives. He was honored by IBM by being named a “Master Inventor” for his 17 patents. In 1994 he was made manager of the Mathematics and Related Computer Science Department at Almaden. 

Dr. Siegel joined the UCSD faculty in 1995 and became the Director of UCSD’s Center for Magnetic Recording Research (CMRR) in 2000. In 2007, Siegel was awarded a CMRR Endowed Professorship at UCSD. Among the many guests at the reception for the endowed professorship were Paul’s wife, Darcy, son Oren and daughter Micah. In addition to the outstanding research Siegel has performed at UCSD, he has trained many Ph.D. students who now populate the storage and communications industries.

Career Timeline:

1980-1995 IBM Almaden Research Laboratory 
1980-1984 Research Staff Member - Developed recording channels for IBM products. 
1984-1993 Project Manager for Signal Processing and Coding. Led R&D effort   on channels.     
1994-1995 Departmental Manager for Mathematics and Related Computer Science. Led research of this group.
1995 – present: Professor in the Department of Electrical and Computer Engineering at  UCSD’s Jacobs School of Engineering.
2000 – present: Director of the Center for Magnetic Recording Research (CMRR), UCSD. 

Awards and Honors:

Member of the National Academy of Engineering
Fellow IEEE 
Editor-in-Chief, IEEE Transactions on Information Theory 
Member, Board of Governors of IEEE Information Theory Society 
1992 IEEE Information Theory Society Prize Paper Award. (co-recipient)
1993 IEEE Leonard G. Abraham Prize Paper Award. (co-recipient)  

Magnetic recording background information:
Advanced data storage systems represent one of the pillars of today's information age. They enable the computing and communication technologies that help drive our economy and improve the quality of our lives. Among the various approaches to storing information, magnetic recording on disks and tapes offers an unmatched combination of large storage capacity, small physical size, random and fast access to data, non-volatility, and low cost. This accounts for the ubiquitous presence of magnetic recording devices in information systems at all scales: central computing facilities, desktop workstations, and portable computers. Increasingly, they are enabling very popular consumer electronics applications, such as digital cameras, "smart" video recording units (such as TiVo), video game machines (such as Microsoft Xbox), and personal digital music players (such as Apple iPod). As of Fall of 2004, over 2 billion disk-drives had been sold, and the growing number of applications such as those just mentioned should push that number to over 3.5 billion within the next few years. 

The 2007 Nobel Prize in Physics went to the researchers who discovered giant magnetoresistance which plays a key role in modern MR (magnetoresistive) read heads. Jacobs School professor and CMRR member Eric Fullerton provides the details here.


The NAE is a private, independent, nonprofit institution. In addition to its role as advisor to the U.S. federal government, the NAE also conducts independent studies to examine important topics in engineering and technology.

Media Contacts

Daniel Kane
Jacobs School of Engineering